Final Four Minutes of Reports
We can deduce:
The Satcom was powered at least until after the last ACARS message, so other systems to keep the plane controllable should have been powered also.
There was not so much flight upset that it took the Satcom antenna out of line of sight of the geostationary satellite, which would have been almost directly overhead. What kind of antenna did it have?
The Satcom antenna was receiving valid steering signals from an IRU to keep it pointed, since it was surely a steered antenna.
GB